The very first UNIX ran on the PDP-7, which had 18-bit words. I happen to have the assembly-language source code to parts of that system. Many programs contain error-handling code that does something like this: lac d1 sys write; 1f; 1 jmp somewhere 1: 077012 ... d1: 1 Evidently the system thought in words in those days (the second argument to sys write is presumably a word count), but the single word written is a strong clue that 9-bit bytes were used, and that a certain concise error message that people love to complain about was there from the beginning (and why not?). Norman Wilson Toronto ON